1. Technical Field
The present invention relates to optical elements and optical modules.
2. Related Art
A surface-emitting type semiconductor laser has characteristics in which its light output changes because temperature dependency occurs in its gain as the temperature of the active layer changes by the influence of surrounding temperatures or the like. For this reason, an optical module that uses a surface-emitting type semiconductor laser may be equipped with a photodetector element that detects a part of laser light emitted from the surface-emitting type semiconductor laser to thereby monitor its light output value. Usually, a photodetector element detects light reflected by a reflector plate that is diagonally provided with respect to an emission direction of the surface-emitting type semiconductor laser.
Also, Japanese Laid Open Patent Application JP-A-10-135568 and non-patent document entitled Vertical Cavity Surface-Emitting Lasers for Optical Data Storage (Jpn. J. Appl. Phys, vol. 35 (1996) pp. 506-507) describe optical elements in which a photodetector element is provided on a top of a surface-emitting type semiconductor laser, whereby a part of laser light emitted from the surface-emitting type semiconductor laser can be monitored within the same element. According to the optical element, the reflector plate described above becomes unnecessary, and miniaturization of the optical element and reduction of the alignment cost can be achieved.
However, in such optical elements, the photodetector element may influence the optical characteristics of the surface-emitting type semiconductor laser.